Uptake and biodegradation kinetics of 2,4-Dichlorophenoxyacetic Acid (2,4-D) from South Saskatchewan River water by an indigenous microbial community

Abstract

The research project entitled "Uptake and Biodegradation Kinetics of 2,4- Dichlorophenoxyacetic Acid (2,4-D) from South Saskatchewan River Water by an Indigneous Microbial Community" was designed to provide insight regarding the persistence of the well-used herbicide, 2,4-D, in Prairie surface water supplies. By examination of the microbial response to the presence of 2,4-D and other water quality conditions, such as pH adjustments and humic acid amendments, in a natural water sample, it was determined that 2,4-D is not likely to be persistent in Saskatchewan surface water. The addition of an acid or base and/or aqueous humic acid to water samples did not significantly affect the uptake and biodegradation kinetics of the indigenous 2,4-D-degrading microbial community. Biodegradation of the 2,4-D parent material was credited to a strain of bacteria minimally identified as Pseudomonas cepacia via microbial isolation techniques, including a known resistance to the anti-biotic, chloramphenicol. It is not presumed that this microbial population was solely responsible for the biodegradation of 2,4-D. This population was merely chosen as the representative, identifiable population in the water samples. Complete mineralisation of the parent compound was confirmed through bi-weekly analyses of dissolved and total organic carbon components and weekly analyses of pH changes in the water samples. The total organic carbon content decreased as carbon dioxide was released from solution indicating complete degradation of the 2,4-D molecule. pH also gradually declined indicating the release of carbon dioxide in the 2,4-D mineralisation process. On average, given the specific conditions examined in these experiments, not more than 40 hours was required to completely mineralize 2,4-D concentrations ranging between 6.5 and 12.5 mg/L.